以下是使用 POSIX 執行緒（pthread）的簡單範例，展示了如何創建和管理多個執行緒。
posix-sched.c

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>  // 引入此標頭以使用 malloc 和 free
#include <unistd.h>  // 引入此標頭以使用 getpid 和 sleep

#define NUM_THREADS 5

/* the thread runs in this function */
void *runner(void *param); 

int main(int argc, char *argv[])  // 修正 main 函數的返回類型
{
    int i, scope;
    pthread_t tid[NUM_THREADS]; 	/* the thread identifier */
    pthread_attr_t attr; 		/* set of attributes for the thread */

    /* get the default attributes */
    pthread_attr_init(&attr);

    /* first inquire on the current scope */
    if (pthread_attr_getscope(&attr, &scope) != 0)
        fprintf(stderr, "Unable to get scheduling scope.\n");
    else {
        if (scope == PTHREAD_SCOPE_PROCESS)
            printf("PTHREAD_SCOPE_PROCESS\n");
        else if (scope == PTHREAD_SCOPE_SYSTEM)
            printf("PTHREAD_SCOPE_SYSTEM\n");
        else 
            fprintf(stderr, "Illegal scope value.\n");
    }
    
    /* set the scheduling algorithm to PCS or SCS */
    if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM) != 0)
        printf("unable to set scheduling policy.\n");

    /* create the threads */
    for (i = 0; i < NUM_THREADS; i++) {
        int *arg = malloc(sizeof(*arg));  // 動態分配記憶體以傳遞執行緒編號
        if (arg == NULL) {
            fprintf(stderr, "Failed to allocate memory.\n");
            exit(1);
        }
        *arg = i;  // 傳遞執行緒編號
        pthread_create(&tid[i], &attr, runner, arg); 
    }

    /**
     * Now join on each thread
     */
    for (i = 0; i < NUM_THREADS; i++) 
        pthread_join(tid[i], NULL);
}

/**
 * The thread will begin control in this function.
 */
void *runner(void *param) 
{
    int thread_id = *((int *)param);  // 取得執行緒編號
    free(param);  // 釋放動態分配的記憶體

    // 獲取當前進程的 PID
    pid_t pid = getpid();
    printf("Thread %d running in process with PID: %d\n", thread_id, pid);

    // 根據執行緒編號執行不同的工作
    printf("Thread %d is doing some work...\n", thread_id);
    sleep(1);  // 模擬工作延遲
    pthread_exit(0);
}

Terminal
編譯並執行

gcc posix-sched.c -o posix-sched -lpthread
./posix-sched

結果：

參考：greggagne/OSC9e/ch6/posix-sched.c